Conventionally, a catheter is retained in a patient's body supplying drug solutions such as carcinostatic drugs and nutrients to a patient's vein temporarily or over a long period of time. In order to use this type of catheter to stably inject drug solutions, it is important that the catheter does not cause infectious diseases or complications as well as does not move and become detached. In addition to that, it is also important that the catheter does not become blocked. However, when using a catheter with an open tip, blood will permeate into the catheter and coagulate resulting in the catheter becoming blocked. In order to prevent the blockage of the catheter due to this blood coagulation, countermeasures have commonly been implemented which fill the inner cavity of the catheter with a Heparinized saline solution. Although this is the case, when implementing this type of countermeasure, there are problems of the actions to retain the catheter in a patient's body becoming cumbersome and complicated causing a burden for the health care professionals and a patient.
Thereupon, conventional catheters with a valve have been provided which are provided with a valve that does not have an open tip and is normally closed only opening when injecting a drug solution between the inside and outside of the catheter and when extracting blood. See, for example, Japanese published unexamined application 560-58167 (patent document 1) and Japanese published unexamined application 2009-273609 (patent document 2). This catheter with a valve (catheter with a bidirectional valve) is made from a flexible elastic material and in addition to the tip being closed, a linear-shaped slit is formed on the tip side. For this reason, when a predetermined differential pressure occurs between the inside and outside of this catheter with a valve, the slit will open allowing the drug solution to be injected into a vein, or the blood within a vein to be flow out into the catheter and extracted. Moreover, when a predetermined differential pressure does not occur between the inside and outside of this catheter with a valve, the slit will maintain the closed state. As a result, coagulation of blood inside the catheter is prevented.
In the conventional catheter with a valve of patent document 1, when a drug solution flows from the outside of the catheter to the inside of the catheter, the slit will open comparatively easy. Although this is the case, when blood flows from the outside of the catheter towards the inside of the catheter, there is a problem of the opposing surfaces forming the slit pressing against each other thereby making it difficult to open the slit.
In the conventional catheter with a valve of patent document 2, a predetermined portion of the tubular body is projected inward and a slit provided there. According to this configuration, the slit becomes comparatively easier to open when blood flows from the outside of the catheter to the inside of the catheter. However, while the release pressure when the valve is opened towards the inside of the catheter becomes lower, the release pressure when the valve is opened towards the outside of the catheter does not become low enough. Because of this, there is still room for improvement as far as the ease of opening is concerned.
The present invention takes the problems mentioned above into consideration and has an objective of providing a catheter with a valve that allows a solution to smoothly flow bi-directionally when a solution flows from the inside of the catheter towards the outside of the catheter and when a solution flows from the outside of the catheter towards the inside of the catheter.